Azimuth control system for towed submersible bodies



March 24, 1964 AZIMUTH Filed March 8. 1957 R. J- ANDERSON CONTROL SYSTEMFOR TOWED SUBMERSIBLE BODIES 2 Sheets-Sheet l ANDERSON INVENTOR.

Zzdfifi; 7,6, WuZZu/ ATTORNEYS March 24, 1964 R. J. ANDERSON 3,125,980

AZIMUTH CONTROL SYSTEM FOR TOWED SUBMERSIBLE BODIES Filed March 8. 19572 Sheets-Sheet 2 005R 0 LEFT PROGRAMMING STEERING MOTOR RAYMOND J.ANDERSON INVENTOR.

BY QM/Z; We M/ AT TORNEYS United States Patent 3,125,930 AZMUTH CONTROLYSTEM FOR TUWED SUBMERSEBLE BODIES Raymond J. Anderson, Pouisbo, Wash,assignor, by mesne assignments, to the United States of America asrepresented by the Secretary of the Navy Filed Mar. 8, 1957, Ser. No.644,960 6 Claims. (Cl. 114-235) This invention relates to towedsubmersible bodies and more specifically to azimuth control systems fortowed submersible bodies.

In the development of towed sonar to detect submarines and the like ithas been found in practice that it is necessary that the towing vehicle,such as for example, a lighter than air airship or surface vessel beable to maneuver quickly when the target takes evasive action. Undersuch circumstances it is essential that the towed sonar faithfully fullyfollow the towing vehicle regardless of any towing maneuver in azimuthto allow tracking of the target and to prevent undesirable stresses inthe towing cables or its connection as a result of such maneuvers.

In the case of airtowed sonar contemplated by the present invention thesonar is suitably mounted in a housing of suitable design that ispreferably both aerodynamically and hydrodynamically stable to insureoptimum conditions for water entry, water exit and towing at the desireddepth. Furthermore, it has been found in practice that such a body mustbe towed from a point intermediate its ends and for the case of anairtowed housing or body the fixed stabilizer surfaces should be ofsuflicient size as to provide aerodynamic stability, which size will begenerally greater than that required for hydrodynamic stability alone.The fixed stabilizer surfaces may be located on the rear portion of thebody as is the conventional practice and as is not the conventionalpractice, provided with a single vertical rudder, hereinafter referredto as a control surface, for horizontal steering of the body.

An object of the invention is to provide a submersible body which can besuccessfully towed by means of a tow line secured to a self-propelledvehicle that will faithfully follow the towing vehicle regardless of anytowing maneuver in azimuth of the towing vehicle.

Another object of the invention is to provide a means for a towedsubmersible body whereby azimuth variations in the direction of travelof the towing vehicle will cause the towed submerged body to faithfullyfollow the towed vehicle.

Still another object of the invention is to provide a simple andimproved azimuth control system for towed submersible bodies.

A further object of the invention is to provide a means of towing asubmersible body beneath and behind a selfpropelled vehicle by means ofa tow line in such a manner that variations in the azimuth heading ofthe towing vehicle will cause the towed body to follow substantiallydirectly astern of the towing vehicle.

These and other objects and features of the invention, together withtheir incident advantages, will be more readily understood andappreciated from the following detailed description of the preferredembodiment thereof selected for purposes of illustration and shown inthe accompanying drawings, in which:

FIGURE 1 generally illustrates to towed submersible housing or body inwhich the invention is employed for detecting and tracking submergedobjects.

FIGURE 2 is a rear View of the body shown in FIG- URE 1 showing in solidlines the normal or straight tow position of the body and in phantomroll positions of the body due to a change in heading or azimuth of thetowing vehicle.

FIGURE 3 is a schematic diagram, party diagrammatic of an on-oi azimuthcontrol system for the submersible body shown in FIGURE 1.

FIGURE 4 is a block diagram of a proportional azimuth control system forthe submersible body shown in FIGURE 1.

Referring now to the drawings and more particularly to FIGURE 1 thereof,there is shown therein a body designated generally by the numeral 16 ofconventional hydrodynamic design having a tow line or cable 11 affixedintermediate the forward and rearward portions of the body to a suitableconnection or tow point 12 by any conventional means. Fixed stabilizersurfaces 13 are provided on the rear portion of the body to render thebody substantially stable when being towed and outwardly extending shortwing stubs 21 are provided at substantially the center middle portion ofthe body 10 to maintain the body at the desired depth. Dynamic and/orstatic stability of the body It) both in air and in water, depending onthe manner and the means by which it is being towed may be secured byproper location of the center of gravity 14 and the tow point 12.

In order to obtain optimum towing conditions and maximum sensitivity forthe present invention a tow point 12 is provided in the middle portionof the body directly above the longitudinal axis and above the center ofgravity 14 such that a lever arm exists either in fact or in theorybetween the center of gravity 14 and the tow point 12. The connection ortow point may be provided at the end of a tow staff (not shown)pivotally mounted about the center of gravity for limited longitudinalmovement or it may be rigidly affixed to or near the upper surface 15 ofthe body as previously described such that any offside tending of thetow line or cable 11 will cause the body 19 to rotate about itslongitudinal axis. A single control surface 16 is pivotally provided inthe upper stabilizer surface 13 for horizontal steering and to opposeany tendency of the body to continue rotation about its longitudinalaxis while in a turn.

The operation and disposition of the body in a straight tow and in aright or left turn is best shown in FIGURE 2. As previously pointed outby proper design the body may be made statically and hydrodynamicallystable. For this reason when the body is being towed on a straightcourse the center of gravity 14, tow point 12 and cable U will lie in asubstantially vertical plane containing the longitudinal axis of thebody and the longitudinal axis of the body will be substantiallyhorizontal, which is to say that the body will travel in a substantiallystraight line with little or no variations in pitch. When the towingvehicle, such as for example, an airship or surface vessel changescourse the towed body will no longer lie directly astern and hence thetow line 11 will assume a new position 171$ to the right or left of itsnormal or ver tical position 19 dependent upon the direction and amountof course change. Due to the dynamic and static stability of the towedbody and the location of the tow points 12, the towed body 10 will berotated about is longitudinal axis during a change in course of thetowing vehicle and the tow point 12 will be thereby simultaneouslyrotated through an angle dependent upon the new position of the tow linewhich is determined by the towing factors, such as for example, depth,towing speed, rate of turn of the towing vehicle and the like.

In practice it has been found preferable to provide stabilizer surfaces13 of conventional design on the rear portion of the body, to disposethe stabilizer surfaces at right angles with each other, two lying in avertical plane and two lying in a horizontal plane, as is conventionalpractice in the art and additionally provide a single control surface 16pivotally mounted in the vertical or upstanding stabilizer surface 13for horizontal steering. A

single control surface 16 for horizontal steering disposed and locatedas previously described performs the dual function of providinghorizontal steering of the body and prevents excessive roll or heel ofthe body in the direction of turn by providing a force or momentopposite in direction to that created by the tow line.

. Sensing and actuating means for the control surface 16 is shown inFIGURE 3 for on-off steering or control. As used herein on-off steeringis distinguished from proportional steering and is of the type whereinthe control surface 16 is thrown from its normal or unactivatedlongitudinally disposed position to full right or full left and viceversa upon a sufficient deviation in course of the towing vehicle.

1 With reference now particularly to FIGURE 3 there is shown two mercuryroll switches 25-26, two return mercury switches 2728, a reversiblesteering motor 29 mechanically connected to the control surface 16 inany convenient manner for pivotal operation thereof, a programming cam31 rotatably operated by the steering motor 29, two mechanicallyactuated roll switches 32-33 and two mechanically actuated returnswitches 34-35 disposed in operative relationship with the programmingcam 31 as will be more fully described hereinafter. For convenience ofexplanation it is assumed that the right roll and left roll as indicatedin FIGURE 3 occurs when viewing the body from rearwardly of thestabilizer surfaces 13, i.e., the right roll is a rotation of the bodyabout its longitudinal axis in a clockwise direction and a left roll isa rotation of the body 10 about its longitudinal axis in acounter-clockwise direction.

The mercury switches 25, 26, 27, 28 are most conveniently mounted withtheir longitudinal axis lying in a plane perpendicular to thelongitudinal axis of the body, such as for example, on a transverseperpendicular dividing wall or bulkhead and the steering motor 29 may beoperably connected to the control surface 16 in any conventional manner,such as for example, by pusher rods and the like and the programming cam31 may be fixedly mounted directly on the armature shaft of the steeringmotor as at 24 or operatively driven by the steering motor through agear train or the like (not shown).

A field winding circuit is shown in FIGURE 3 comprised of a right rollmercury switch 25 and a left roll mercury switch 26 connected in serieswith one terminal of a source of electric current 36 such as a batteryor the like and in series respectively with a normally closed right rollmechanical switch 32 and a normally closed left roll mechanical switch33 which are each separably connected respectively to an end terminal37-38 of the field winding 39 of the steering motor 29. Two returnmercury switches 27-28 are connected in series with each other and thesource of current 36 and terminal 41 of a motor damping resistor 42. Theremaining terminal 43 of the damping resistor 42 is connected to twonormally open mechanical switches 3435 which are each connectedrespectively to the end terminals 3738 of the field winding 39.

The mercury switches 25, 26, 27, 28 may be of conventional form whereina change of position is necessary to open or close the switch and, ifdesired, may be additionally provided with suitable means or formed suchthat splashing of the mercury will be substantially prevented therebyreducing the possibility of undesirable operation of the steering motorduring extreme operating or towing conditions.

The mechanically operable roll switches 3233 and the mechanicallyoperable return switches 34-35 may be of the type commonly referred toand well known in the art as microswitches and are fixedly mounted inthe same plane as the programming cam 31 and disposed in operablerelationship therewith. The programming cam 31 is of the planar varietyhaving an enlarged first portion 44 provided with a relatively longannular surface 45, a

generally rectangular second portion 46 integral with portion 44 and ofreduced size extending in a direction substantially opposite to theannular surface 45 and adapted for rotation about point 24, as bymounting the cam on the armature shaft of the steering motor. Mechanicalswitches 3233 and 34-35 are fixedly disposed away from the programmingcam 31 such that they will be unactivated when the programming cam is inits normally unactivated position but will be actuated in apredetermined manner upon rotation of the programming cam. Uponcounter-clockwise rotation of the programming cam the annular surface 45will be moved to a position to close switch 35 prior to the time portion46 arrives at a position suflicient to open switch 32. Obviously, aclockwise rotation of the programming cam from its full counterclockwiseposition will cause switch 32 to close prior to the time it will causeswitch 35 to open. An initial rotation of the programming cam from itsnormally unactuated position in a clockwise direction will result inoperation of switches 34-33 in substantially the same manner aspreviously described herein above for switches 32-35.

When the body is in its normal towing position the return mercuryswitches 27-28 are closed and the right roll mercury switch 25 and theleft roll mercury switch 26 are open, but no current is fed to the fieldwinding 39 of the steering motor 29 due to the fact that the returnmechanical switches 3435 are unactivated and in their normally openposition. The four mercury switches 25, 26, 27, 28 are mounted aspointed out hereinbefore such that they will not be actuated until sucha time as the body exceeds a critical degree of roll such as forexample, three degrees. When the body assumes an angular positionsufficiently to the right for example, the right roll mercury switch 25will close and the return mercury switch 28 will open. Due to the factthat the right roll mechanical switch 32 is unactivated and in itsnormally closed position, current is allowed to flow through one half ofthe center tapped field winding 39, thereby energizing the steeringmotor for rotation in a predetermined direction. The direction ofrotation of the armature shaft of the steering motor may be selectedsuch as to cause the programming cam 31 to rotate in a counter-clockwisedirection and since the steering motor is operated under full power, theprogramming cam 31 will be moved to its full counter-clockwise positionand the control surface 16 will be moved to its full right position.Rotation of the programming cam 31 in a counter-clockwise directioncauses the return mechanical switch 35 to be closed, and the right rollmechanical switch 32 to be opened, thus breaking the circuit to thefield winding 39 of the steering motor and stopping the motor, thecontrol surface 16 consequently remaining in its full right position. Itmay now be obvious that return mechanical switch 35 having beenpreviously closed by the programming cam 31, when the right roll isrelieved, the return mercury switches 27-28 will both be closed therebyallowing current to be applied only to the opposite portion of the fieldwinding thereby causing the steering motor to rotate in a directionopposite to its previous direction and return the control surface 16 toits normal position. Due to the reversal of direction of rotation of thearmature of the steering motor the programming cam 31 will be caused tonow rotate in a clockwise direction thus allowing the right rollmechanical switch 32 to assume its normally closed position andsimultaneously allowing the return mechanical switch 35 to assume itsnormally open position thus removing all current from the field winding39 of the steering motor. Due to the inertia of the armature shaft ofthe motor, the programming cam will move past its center or normalposition and close the return mechanical switch 34 thus causing themotor to again reverse its direction of rotation since the returnmercury switches 27-28 are closed. Exact centering of the controlsurface 16 is accomplished by the action of the programming cam 31opening and closing the return mechanical switches 3435. In order toeliminate continuous oscillation of the control surface 16 due toinertia of the motor armature shaft, a damping resistor 42 is providedin series with each half of the field winding 39 of the steering motor.The function of the damping resistor 42 is to reduce the startingcurrent to the steering motor thus dampening the oscillations of thearmature shaft at the center or normal position and thereby causing themotor to come to rest in a very short time at the neutral position withthe system de-energized.

Due to the symmetry of the field winding circuit it may now be obviousthat the description given above is equally applicable for a left rollexcept that the operation of the right roll mercury switch 25, the leftroll mercury switch 26 and return mercury switches 2728 are reversed, asis the direction of rotation of the programming cam 3 1, Le, for a leftroll the programming cam 31 is rotated from its normal position in aclockwise direction and the control surface '16 is rotated to the left.

Sensing and actuating means for a proportional control system is shownin block form in FIGURE 4. As used herein, proportional control hasreference to that type of control wherein the degree of control surfacemovement is proportional to the amount of actuating or error signal. Fora proportional system as shown in FIG- URE 4 a vertical gyroscope 51adapted and disposed to sense roll errors may be provided to actuate awheatstone bridge motor control circuit 52 for proportional operation ofa steering motor 53 mechanically connected to the control surface 16 inany suitable manner as described previously hereinabove. -Apotentiometer (not shown) actuated by the gyro 5 1 may form theactuating arm of the wheatstone bridge motor control circuit similar tothat shown and described in patent application Serial No. 587,180, nowPatent No. 3,045,627, filed May 24, 1956, to which reference is herebymade.

It may now be obvious that the movement of the control surface 16 willbe in direct proportion to the amount of roll sensed by the gyro 51,varying from maximum roll and maximum control surface movement to noroll and no control surface movement, thereby resulting in relativelysmooth changes in course of the body when required by a change in courseof the towing vehicle.

It may now be seen that the present invention provides a horizontal orazimuth control system for a submersible body adapted to be submersiblytowed by a surface or airborne vehicle wherein the location and type oftow cable connection and the characteristics of the body cooperate in aunique manner with roll error sensing means to provide accurate andsensitive horizontal control of the towed body thereby causing it tofollow, especially when submerged, directly astern of the towing vehicleregardless of any towing maneuver in azimuth involved, as searching forand/ or tracking a surface or submerged target.

While the invention has been described in detail with the reference tothe detection of dirigible surface or submerged objects, such as forexample, ships and submarines, it is obviously not so 'limited as it maybe employed to advantage in any towed submersible body wherein it isdesired that the body faithfully follow the towing vehicle in azimuth.

Whilethe present invention has been described in its preferredembodiment it is realized that modifications may be made, it is desiredthat it be understood that no limitations upon the invention areintended other thanmay be imposed by the scope of the appended claims.

Having now disclosed my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. In a towed submersible body having a control surface disposed forhorizontal steering and adapted to be towed from a point about thecenter of gravity and lying in a longitudinal plane passing through thecenter of gravity and the center portion of the body an azimuth controlsystem comprising: a source of current; an electric motor operablyassociated wth said control surface; and a field winding circuitconnected to said source of current for actuating said electric motor,said field winding circuit comprising a motor field winding and meanssensitive to a change of position about the longitudinal axis of saidbody connected to said field winding whereby a change in position ofsaid body about its longitudinal axis will cause actuation of saidmotor.

2. In a towed submersible body having an upstanding pivotally mountedcontrol surface and adapted to be towed from a point above the center ofgravity and lying in a vertical longitudinal plane passing through thecenter of gravity and the center portion of the body an azimuth controlsystem comprising: a source of current; a rever sible electric motoroperably associated with said control surface; and a field windingcircuit connected to said source of current for actuating said electricmotor, said field winding circuit comprising a motor field winding andmeans sensitive to a change of position about the longitudinal axis ofsaid body connected to said field winding whereby a change in positionof said body about its longitudinal axis will cause actuation of saidmotor.

3. In a towed submersible body having an upstanding pivotally mountedcontrol surface and adapted to be towed from a point above the center ofgravity and lying in a vertical longitudinal plane passing through thecenter of gravity and the center portion of the body an azimuth controlsystem comprising: a source of current; a reversible electric motoroperably associated with said control surface; and a field windingcircuit connected to said source of current for actuating said electricmotor, said field winding circuit comprising a motor field winding andmeans operatively sensitive to an angular change of position connectedto said field winding whereby an angular change in position of said towpoint will cause actuation of said control surface in the direction ofsaid angular change of position of said tow point.

4. In an elongated body hydrodynamically and aerodynamically stablehaving a front portion, a rear portion and a smooth upper surface andadapted to be towed by a cable from a self-propelled vehicle an azimuthcontrol system comprising: a tow point disposed intermediate the frontportion and the rear portion and above the center of gravity of saidbody and lying in a vertical longitudinal plane passing through thecenter of gravity of said body; an upstanding control surface pivotallycarried by said rear portion; a source of electric current; a reversibleelectric motor operably connected to said control surface; and a motorfield winding circuit for controlling said motor and connected to saidsource of current comprising a field winding and means operativelysensitive to an angular change of position of said tow point.

5. In an elongated body hydrodynamically and aerodynamically stablehaving a front portion, a rear portion and a smooth upper surface andadapted to be towed by a cable from a self-propelled vehicle an azimuthcontrol system comprising: a tow point disposed intermediate the frontportion and the, rear portion and above the center of gravity of saidbody and lying in a vertical longitudinal plane passing through thecenter of gravity of said body; an upstanding control surface pivotallycarried by said rear portion; a source of electric current; a reversibleelectric motor operably connected to said control surface; and a motorfield winding circuit for controlling said motor and connected to saidsource of current comprising a field winding, a gyroscope adapted toproduce an error signal proportional to the amount of angulardisplacement of said tow point, and wheatstone bridge means disposedbetween said gyroscope and said field Winding whereby the direction ofrotation and actuation of said motor is controlled by said error signal.

6. In an elongated body hydrodynamically and aerodynamically stablehaving a front portion, a rear portion and a smooth upper surface andadapted to be towed by a cable from a self-propelled vehicle an azimuthcon trol system comprising: a tow point disposed intermediate the frontportion and the rear portion and above the center of gravity of saidbody and lying in a vertical longitudinal plane passing through thecenter of gravity of said body; an upstanding control surface pivotallycarried by said rear portion; a source of electric current; a reversibleelectric motor operably connected to said control surface; and a motorfield winding circuit for controlling said motor and connected to saidsource of current comprising a field winding, first and second switchmeans normally open and operable upon a predetermined angular change ofposition, third and fourth switch means normally closed and operableupon a pre- References Cited in the file of this patent UNITED STATESPATENTS 2,359,366 Katcher Oct. 3, 1944 2,411,156 Grimminger Nov. 19,1946 3,086,490 Nichols Apr. 23, 1963

1. IN A TOWED SUBMERSIBLE BODY HAVING A CONTROL SURFACE DISPOSED FORHORIZONTAL STEERING AND ADAPTED TO BE TOWED FROM A POINT ABOUT THECENTER OF GRAVITY AND LYING IN A LONGITUDINAL PLANE PASSING THROUGH THECENTER OF GRAVITY AND THE CENTER PORTION OF THE BODY AN AZIMUTH CONTROLSYSTEM COMPRISING: A SOURCE OF CURRENT; AN ELECTRIC MOTOR OPERABLYASSOCIATED WTH SAID CONTROL SURFACE; AND A FIELD WINDING CIRCUITCONNECTED TO SAID SOURCE OF CURRENT FOR ACTUATING SAID ELECTRIC MOTOR,SAID FIELD WINDING CIRCUIT COMPRISING A MOTOR FIELD WINDING AND MEANSSENSITIVE TO A CHANGE OF POSITION ABOUT THE LONGITUDINAL AXIS OF SAIDBODY CONNECTED TO SAID FIELD WINDING WHEREBY A CHANGE IN POSITION OFSAID BODY ABOUT ITS LONGITUDINAL AXIS WILL CAUSE ACTUATION OF SAIDMOTOR.